This invention relates to a disc player such as an optical video disc player.
Recently, it has been proposed to reproduce signals on both faces of an optical video disc without reversing it on a turntable. FIG. 1 shows the construction of such a player. A disc 1 is placed on a turntable 4. When a spindle motor 2 is energized, a spindle 3 and hence the turntable 4 are rotated together with the disc 1. A pickup 5A is disposed on the side of the turntable 4 when the face A of the disc 1 is to be reproduced, and another pickup 5B is disposed on the side opposite to the turntable 4 when the face B is to be reproduced.
In any case, the disc has been centered as shown in FIG. 2. More specifically, a centering hub 6 is mounted at the inner periphery of the turntable 4. The centering hub 6 is urged upwardly in the Figure by a spring 7. Numeral 8 denotes a ring for preventing the separation of the centering hub 6 urged by the spring 7.
When the disc 1 is placed on the turntable 4, a tapered surface of the outer periphery of the centering hub 6 is engaged with an edge of a center hole of the disc 1, so that the disc 1 is centered in such a manner that the center of the center hole if brought into alignment with the center of rotation of the spindle 3.
Thus, in the conventional player, in the case where the pickup disposed on either side is to be used, the disc 1 is centered by the centering hub 6 mounted on the turntable 4. However, since the optical video side is formed into one disc capable of double-faced reproduction by bonding together two discs each having signals recorded on its one face, center holes of the bonded two discs do not always coincide with each other accurately. Therefore, even if the centering is effected by the centering hub 6, the center of the center hole of the disc on the side opposite to the turntable 4 (upper side) is not in alignment with the center of rotation of the spindle 3. As a result, when the signals are to be reproduced by the pickup 5B disposed on the side opposite to the turntable 4, the eccentricity of the disc becomes greater, and in the worst case, a tracking servo is liable to become disabled, and the reproduction has sometimes virtually been impossible.